Vivaldi was prolific, composing vast quantities of instrumental and vocal music and nearly 50 operas. Of the 500 concertos he wrote, the most popular in his life-time as well as today were the four known as Le Quattro Stagioni - The Four Seasons, works that had circulated widely in manuscript before being published in Amsterdam in 1725, when explanatory poems were added to clarify the programme of each concerto. The set was dedicated to Count Wenzel von Morzin, a cousin of Haydn's first patron. The title page describes Vivaldi himself as the Count's "maestro in Italia", as "Maestro de' Concerti" of the Pieta, as well as "Maestro di Capella di Camera" of Prince Philip, Land grave of Hesse-Darmstadt.